91 is an odd composite number composed of two prime numbers multiplied together.

What does the number 91 look like?

This visualization shows the relationship between its 2 prime factors (large circles) and 4 divisors.

91 is an odd composite number. It is composed of two distinct prime numbers multiplied together. It has a total of four divisors.

Prime factorization of 91:

7 × 13

See below for interesting mathematical facts about the number 91 from the Numbermatics database.

Names of 91

  • Cardinal: 91 can be written as Ninety-one.

Scientific notation

  • Scientific notation: 9.1 × 101

Factors of 91

  • Number of distinct prime factors ω(n): 2
  • Total number of prime factors Ω(n): 2
  • Sum of prime factors: 20

Divisors of 91

  • Number of divisors d(n): 4
  • Complete list of divisors:
    1 7 13 91
  • Sum of all divisors σ(n): 112
  • Sum of proper divisors (its aliquot sum) s(n): 21
  • 91 is a deficient number, because the sum of its proper divisors (21) is less than itself. Its deficiency is 70

Bases of 91

  • Binary: 10110112
  • Hexadecimal: 0x5B
  • Base-36: 2J

Squares and roots of 91

  • 91 squared (912) is 8281
  • 91 cubed (913) is 753571
  • The square root of 91 is 9.5393920141
  • The cube root of 91 is 4.4979414453

Scales and comparisons

How big is 91?
  • 91 seconds is equal to 1 minute, 31 seconds.
  • To count from 1 to 91 would take you about forty-five seconds.

    This is a very rough estimate, based on a speaking rate of half a second every third order of magnitude. If you speak quickly, you could probably say any randomly-chosen number between one and a thousand in around half a second. Very big numbers obviously take longer to say, so we add half a second for every extra x1000. (We do not count involuntary pauses, bathroom breaks or the necessity of sleep in our calculation!)

  • A cube with a volume of 91 cubic inches would be around 0.4 feet tall.

Recreational maths with 91

  • 91 backwards is 19
  • The number of decimal digits it has is: 2
  • The sum of 91's digits is 10
  • More coming soon!

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The information we have on file for 91 includes mathematical data and numerical statistics calculated using standard algorithms and methods. We are adding more all the time. If there are any features you would like to see, please contact us. Information provided for educational use, intellectual curiosity and fun!

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